1. Field of the Invention
This invention relates generally to improvements in monitoring methods and apparatus and more particularly to methods and apparatus for monitoring or logging the parameters of conditions encountered during the course of drilling a well .
2. Description of the Prior Art
During various drilling operations particularly those related to the rotary drilling of an oil or a gas well, a drilling fluid is commonly circulated and partially retained in the borehole for various reasons, as for example, to exert hydrostatic pressure to keep the gas pressure substantially sealed in the borehole and to remove drill bit cuttings from the borehole. During the startup of the drilling operation and during the drilling operations themselves, it is important that the operator have available certain information including that relating to the flow of the drilling fluid so that the operator will be in a position to quickly and intelligently make certain operational or procedural decisions relating to the drilling operation. For example, the rate the drilling fluid is being pumped into the borehole, volume of the drilling fluid in the fluid pits and the rate the drilling fluid is being returned to the fluid pits constitutes some of the drilling fluid parameters needed by the operator.
The above mentioned drilling fluid parameters provide an indication to the operator of certain possible problems which may exist at various times during the drilling operations. For example, an increase of the volume of drilling fluid in the fluid pits may indicate a possible "blow out", and thereby provide a basis for an operator's decision to increase the weight of the drilling fluid being circulated into the borehole. On the other hand a decrease in volume of the drilling fluid may indicate a possible loss of drilling fluid in the formation, a condition commonly referred to as "loss-circulation". Further a knowledge of the relative flow of drilling fluid in the return flow line generally indicates to the operator such conditions, as for example, that the borehole is stable and drilling operations may be conducted.
Other parameters usually measured during the drilling operations include hook load, weight on bit, and rotary rate standpipe pressure and rotary torque which with rate of penetration are helpful in determining the optimum values of the stated parameters to efficiently and safely drill the various subsurface formations.
Various solutions have been offered in the past to provide an operator with some if not with all of the aforementioned parameters or data. However, as drilling operations have become more complex and sophisticated due to efforts to locate hydrocarbons at increasing depths, it has become more important that the operator have available in an immediate and usable form the maximum drilling data which includes sufficient drilling-fluid parameters upon which the various operational decisions can be quickly and efficiently based.
Sophisticated design has led to the utilization of computers or micro processors which in known systems have been made the heart of such systems in that data received from various sensors located about the drilling system are first fed to the micro processors where the data are converted to binary form and thereafter transmitted to visual display devices including LED display and chart recorders. The disadvantage of such systems lies in the fact that when the micro processor goes down for one reason or another the operator is effectively blind in conducting the drilling operations and until the micro processor is returned to a useful state, a potentially hazardous condition exists during which time the operator is unable to know what if any corrective action to take upon the occurrence of a sudden change in drilling conditions.
In addition to merely monitoring the existing drilling conditions, it is also desirable that the drill site geologist and engineer have the capability of utilizing the parameters in further analysis of the drilling conditions such for example as critical velocity, slip velocity, and equivalent circulating density.
Accordingly it becomes important that in view of the size and complexity of modern drilling rig systems that a reliable, accurate system be provided of monitoring and analyzing drilling parameters more efficiently and with added safety to conduct well drilling operations.